1. Field of Invention
The present invention relates to a failure diagnosis method for a brake system of a vehicle driven using an electric motor. More particularly, the present invention relates to a failure diagnosis method for a brake system of a vehicle, in which, when a failure occurs in the brake system of the vehicle, it is decided whether the failure occurs in any one of a regenerative braking device, a front-wheel friction braking device and a rear-wheel friction braking device, which constitute the brake system.
2. Description of Related Art
As known in the art, a green vehicle such as a hybrid vehicle or electric vehicle driven by an electric motor performs regenerative braking to improve fuel efficiency when a driver stops the vehicle.
In general, a regenerative braking system of the green vehicle converts kinetic energy of the vehicle into electric energy, stores the converted electric energy in a battery, and enables the electric energy stored in the battery to be reused while driving an electric motor, thereby improving the fuel efficiency of the vehicle.
The vehicle performs regenerative braking cooperation control which allows the sum of a regenerative braking torque generated in an electric motor (driving motor) and a friction braking torque generated in a brake during regenerative braking to be equal to a driver's required braking torque.
However, the braking force generated in the vehicle when a failure occurs in a regenerative braking device or friction braking device (i.e., the braking force of the vehicle) does not satisfy the driver's required braking force (does not generate a braking force corresponding to the driver's required braking force). Therefore, the driver feels different when the braking of the vehicle is performed, and the braking distance of the vehicle is increased.
In order to prevent such a situation, a device for detecting a failure of each braking device and compensating for a braking force of the device in which the failure occurs is mounted in the braking device of the vehicle.
Conventionally, there was used a failsafe control method of a braking device, which can satisfy a driver's required braking force by determining a failure of a corresponding braking device, using a signal transmitted from the braking device when a failure occurs in the braking device built in a vehicle, and compensating for a braking force of the braking device in which the failure occurs.
However, in a case where the failure decision signal of the braking device is not used in the conventional fail safe control method, the compensation for the braking force of the braking device in which the failure occurs is not performed, and therefore, a braking force corresponding to the driver's required braking force is not generated.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.